John Calvin Commentary Isaiah 58:6

"Is not this the fast that I have chosen: to loose the bonds of wickedness, to undo the bands of the yoke, and to let the oppressed go free, and that ye break every yoke?" — Isaiah 58:6 (ASV)

Is not this the fast which I have chosen? The Prophet shows what the real duties of piety are, and what God chiefly recommends to us: namely, to relieve those who are wretched and pressed with a heavy burden. But the Prophet appears to abolish fasting universally when, in place of it, he enumerates those works that are most highly acceptable to God.

I reply, fasting is approved when it is accompanied by the love we owe our neighbors. Therefore, the Prophet directs that we should be tested by this principle: that our consciences are whole and pure, and that we show mutual kindness to each other. For if this order prevails, then fasting, added to it, will be pleasing and acceptable to God.

But here he makes no mention of purity of heart. I reply, it is described by works, as by its fruits, from which it is easily seen what kind of heart we have. Next, he enumerates the duties of the Second Table, under which, as we have seen elsewhere, by a figure of speech in which a part is taken for the whole, he includes the whole observance of the Law. For it would not be enough to assist our neighbor with kind deeds if, at the same time, we despised God.

But we must note the Prophet’s purpose, because the love we owe our neighbors cannot be sincerely cultivated unless we love them in God. To test our fear of God, he requires these as more direct signs: whether we live justly, harmlessly, and kindly with each other.

Besides, he was not satisfied with outward appearance; indeed, the love of our neighbor does not thrive where the Spirit of God does not reign. Therefore, Paul includes it in the enumeration of “the works of the Spirit” (Galatians 5:22). Thus, when the observance of the Law is spoken of, not only outward works but also the dispositions of the heart must be taken into account.

To loose wicked bindings. Some explain this phrase to mean “sinful thoughts,” by which people's hearts are entangled. But Isaiah appears to me to have had another purpose in mind: namely, that hypocrites are exceedingly cruel in distressing the poor and lay heavy burdens on them. He therefore calls these things “bonds,” or “bindings,” or, as we commonly say, “oppressions.” What he adds has the same significance: to undo the heavy burdens, under the weight of which the poor groan and are overwhelmed. He again adds, to let the oppressed go free, and expresses the same idea in various ways. Thus, the Prophet does not define what is meant by “fasting,” but shows what the Lord requires first and foremost, how our obedience can be approved by Him, and what the dispositions should be of those who endeavor to fast correctly.